Lower Blood Pressure
Spearmint contains the compound (-)-carvone. Studies have shown that this compound behaves in ways similar to ingredients found in high blood pressure medication. One study on animals that showed that (-)-carvone reduces blood vessel contractions, though it may be too soon to tell if the same would be found in humans.
 
Help with Digestive Issues
Spearmint may also contribute to a healthier stomach and alleviate symptoms like nausea. Spearmint tea may be able to help your stomach muscles relax, helping these and other digestive problems subside.
 
Improved Memory
Spearmint tea may also help improve your memory. One study showed that older people with memory issues who were given daily spearmint extract supplements saw a 15 % improvement in their memory.
 
Lower Blood Sugar
There may also be properties in spearmint tea that lower blood sugar and help people who have diabetes maintain their health. While no extensive study has been done on humans to investigate these benefits, studies on rats with diabetes have shown lower blood sugar levels when given spearmint.
 
Source:  https://www.webmd.com/diet/spearmint-tea-health-benefits